U.S. patent number 10,629,859 [Application Number 15/559,857] was granted by the patent office on 2020-04-21 for coin-shaped battery.
This patent grant is currently assigned to PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.. The grantee listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to Tadayoshi Takahashi, Tomohiro Yagishita.
United States Patent |
10,629,859 |
Yagishita , et al. |
April 21, 2020 |
Coin-shaped battery
Abstract
A coin type battery includes: a battery case having a bottom
plate and a side portion rising from a rim of the bottom plate; a
sealing plate having a top plate and a rim portion extending from
the top plate to the inside of the side portion; a gasket
compressed and interposed between the side portion and the rim
portion; and a power generation element sealed by the battery case
and the sealing plate. At least one of the battery case and the
sealing plate includes a plated layer disposed on the outer surface
side, and a substrate layer disposed on the inner surface side of
the plated layer. The plated layer includes at least two metals
selected from a set consisting of nickel, zinc, and tin.
Inventors: |
Yagishita; Tomohiro (Osaka,
JP), Takahashi; Tadayoshi (Osaka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka |
N/A |
JP |
|
|
Assignee: |
PANASONIC INTELLECTUAL PROPERTY
MANAGEMENT CO., LTD. (Osaka, JP)
|
Family
ID: |
59311286 |
Appl.
No.: |
15/559,857 |
Filed: |
December 16, 2016 |
PCT
Filed: |
December 16, 2016 |
PCT No.: |
PCT/JP2016/005160 |
371(c)(1),(2),(4) Date: |
September 20, 2017 |
PCT
Pub. No.: |
WO2017/122250 |
PCT
Pub. Date: |
July 20, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180062119 A1 |
Mar 1, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Jan 12, 2016 [JP] |
|
|
2016-003585 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M
2/0292 (20130101); H01M 2/0257 (20130101); H01M
2/0222 (20130101); H01M 2/026 (20130101); H01M
2/0413 (20130101); H01M 2/08 (20130101) |
Current International
Class: |
H01M
2/02 (20060101); H01M 2/08 (20060101); H01M
2/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
1447458 |
|
Oct 2003 |
|
CN |
|
101171700 |
|
Apr 2008 |
|
CN |
|
103718331 |
|
Apr 2014 |
|
CN |
|
59-046756 |
|
Mar 1984 |
|
JP |
|
4-312762 |
|
Nov 1992 |
|
JP |
|
2008-539553 |
|
Nov 2008 |
|
JP |
|
2010-508641 |
|
Mar 2010 |
|
JP |
|
Other References
International Search Report of PCT application No.
PCT/JP2016/005160 dated Feb. 21, 2017. cited by applicant .
English Translation of Chinese Search Report dated Nov. 5, 2019 for
the related Chinese Patent Application No. 201680023397.3. cited by
applicant.
|
Primary Examiner: Domone; Christopher P
Attorney, Agent or Firm: McDermott Will & Emery LLP
Claims
The invention claimed is:
1. A coin type battery comprising: a battery case having a bottom
plate and a side portion rising from a rim of the bottom plate; a
sealing plate having a top plate and a rim portion extending from
the top plate to an inside of the side portion; a gasket compressed
and interposed between the side portion and the rim portion; and a
power generation element sealed by the battery case and the sealing
plate, wherein: at least one of the battery case and the sealing
plate includes: a substrate layer having a first surface and a
second surface opposite to the first surface; and a plated layer
plated on the first surface layer of the substrate, the plated
layer is disposed on an outer surface side of the coin type
battery, the substrate layer is disposed closer to the power
generation element than the plated layer, and the plated layer
includes nickel, and further includes at least one selected from
the group consisting of zinc and tin.
2. The coin type battery according to claim 1, wherein the plated
layer includes nickel by 30 mass % or less.
3. The coin type battery according to claim 1, wherein the plated
layer includes nickel by 5 to 20 mass %.
4. The coin type battery according to claim 1, wherein the plated
layer includes at least tin and zinc.
5. The coin type battery according to claim 4, wherein the plated
layer includes zinc by 35 mass % or less.
6. The coin type battery according to claim 1, wherein a thickness
of the plated layer is 0.5 to 10 .mu.m.
7. The coin type battery according to claim 1, wherein the
substrate layer includes stainless steel.
8. The coin type battery according to claim 1, wherein a Ni plated
layer is further plated on the second surface of the substrate
layer.
Description
This application is a U.S. national stage application of the PCT
International Application No. PCT/JP2016/005160 filed on Dec. 16,
2016, which claims the benefit of foreign priority of Japanese
patent application 2016-003585 filed on Jan. 12, 2016, the contents
all of which are incorporated herein by reference.
TECHNICAL FIELD
The present invention relates to a coin type battery, and more
specifically to a coin type battery having a high safety from
accidental ingestion or swallow.
BACKGROUND ART
Coin type batteries are widely used as power sources for small
apparatuses or memory backup. The application of the coin type
batteries is continually expanded. So, countermeasures against
accidental ingestion of a coin type battery become more important.
When a coin type battery has been ingested or swallowed into a
living body, the terminal surface of each of a case and a sealing
plate of the coin type battery comes into contact with a body
fluid, thereby promoting the electrolysis of water. The pH of body
fluid is around neutral. As the electrolysis of water proceeds, the
body fluid near the terminal surface on the negative electrode side
shifts to alkaline, and the body fluid near the terminal surface on
the positive electrode side shifts to acidic. Therefore, the living
body is damaged.
From the viewpoint of preventing accidental ingestion, Patent
Literature 1 proposes the production of a conductive film
containing a bitter substance on a battery surface.
CITATION LIST
Patent Literature
PTL 1: Unexamined Japanese Patent Publication No. H04-312762
SUMMARY OF THE INVENTION
However, in the case of ingestion of a coin type battery into a
living body without spitting out, the method of Patent Literature 1
is difficult to prevent the above mentioned damage.
From the above-mentioned problems, the objective of the present
disclosure is to provide a highly safe coin type battery that can
reduce the damage to a living body by accidental ingestion.
A coin type battery of the present disclosure includes the
following components:
a battery case having a bottom plate and a side portion rising from
a rim of the bottom plate;
a sealing plate having a top plate and a rim portion extending from
the top plate to the inside of the side portion;
a gasket compressed and interposed between the side portion and the
rim portion; and
a power generation element sealed by the battery case and the
sealing plate.
At least one of the battery case and the sealing plate includes a
plated layer disposed on the outer surface side, and a substrate
layer disposed on the inner surface side of the plated layer. The
plated layer includes at least two metals selected from a set
consisting of nickel, zinc, and tin.
The present disclosure can reduce the damage to a living body by
accidental ingestion of a coin type battery.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a vertically sectional view of a coin type battery in
accordance with an embodiment of the present invention.
DESCRIPTION OF EMBODIMENT(S)
A coin type battery of embodiments of the present invention
includes a power generation element, and an exterior body for
sealing and storing the power generation element. The exterior body
includes the following components:
a bottomed battery case having an opening;
a sealing plate for blocking the opening in the battery case;
and
a gasket interposed between an end (opening end) of a side portion
of the battery case and a rim portion of the sealing plate.
The power generation element includes: a first electrode; a second
electrode; a separator interposed between them; and an electrolyte.
The power generation element is filled into a space formed of the
battery case and the sealing plate. Then, the opening end of the
battery case is caulked to the rim portion of the sealing plate via
the gasket. Thus, the power generation element is sealed and stored
in the exterior body. The coin type battery includes not only a
coin-shaped battery but also a button-shaped battery. In other
words, the shape and diameter of the coin type battery are not
particularly limited. For example, the coin type battery of the
present invention also includes a button-shaped battery whose
thickness is greater than the diameter.
In more detail, the battery case includes a bottom plate, and a
side portion rising from the rim of the bottom plate. The bottom
plate normally has a circular shape, but may have a shape (for
example, elliptical shape) close to the circular shape. The sealing
plate includes a top plate, and a rim portion extending from the
top plate to the inside of the side portion of the battery case.
The top plate corresponds to the shape of the bottom plate, and has
a circular shape having a diameter smaller than that of the bottom
plate. Thickness T of the coin type battery is often normally
smaller than diameter D of the bottom plate (T<D). For example,
1.2 mm.ltoreq.T.ltoreq.5.0 mm, and 9 mm.ltoreq.D.ltoreq.24.5 mm are
established. The gasket is compressed and interposed between the
side portion of the battery case and the rim portion of the sealing
plate. In this, at least one of the battery case and the sealing
plate includes a plated layer disposed on the outer surface side.
The plated layer includes at least two metals selected from a set
consisting of nickel, zinc, and tin.
The polarity of the first electrode is different from that of the
second electrode. So, when the first electrode is a positive
electrode (or negative electrode), the second electrode is a
negative electrode (or positive electrode). When the coin type
battery is a lithium battery, the positive electrode is stored in
the exterior body so as to face the bottom plate of the battery
case, and the negative electrode is stored in it so as to face the
top plate of the sealing plate. The arrangement of the positive
electrode and negative electrode is not limited to this.
The plated layer disposed on the outer surface of the battery case
or sealing plate includes at least two metals selected from a set
consisting of nickel, zinc, and tin. In the case of accidental
ingestion or swallow of the coin type battery, on the negative
electrode side, the plated layer suppresses the water electrolysis
reaction by a contact of the sealing plate with a body fluid. On
the positive electrode side, the plated layer suppresses the
corrosion reaction of the battery case.
Usually, the exterior body of a coin type battery is made of
stainless steel having a nickel-plated layer on its outer surface.
In the case of accidental ingestion of the coin type battery having
this exterior body, the electrolysis reaction of water proceeds in
the body. In other words, on the negative electrode side, hydrogen
is generated by the electrolysis of water, and the body fluid
shifts to the alkaline side. As a result, the nickel on the outer
surface dissolves to expose the stainless steel to the outside.
Stainless steel has a hydrogen overvoltage lower than that of
nickel, so that the water electrolysis reaction is more activated
and the body fluid around the negative electrode shifts to a strong
alkaline side. While, on the positive electrode side, the nickel
and stainless steel are dissolved by a corrosion reaction, and the
body fluid around the positive electrode shifts to a strong acid
side.
In the present invention, a plated layer containing at least two
metals selected from a set consisting of nickel, zinc, and tin is
disposed on the outer surface side of a substrate layer in the
sealing plate that is electrically connected to the negative
electrode or in the battery case that is electrically connected to
the positive electrode.
In the case that the sealing plate includes the plated layer, a
local battery reaction between metals having different ionization
tendencies proceeds in the plated layer, and a dissolving reaction
is suppressed. Therefore, the exposure of the substrate layer to
the outside can be prevented, and the generation of hydrogen can be
significantly suppressed. Furthermore, the hydrogen overvoltage of
tin or zinc is higher than that of nickel, so that the water
electrolysis reaction rate on a surface of the plated layer can be
reduced. As a result, the shift of the body fluid around the
negative electrode to a strong alkaline side is significantly
reduced.
While, in the case that the battery case includes the plated layer,
the dissolution of the plated layer by a corrosion reaction is
suppressed, so that the shift of the body fluid around the positive
electrode to a strong acid side can be suppressed. In a normal
battery case, the substrate layer is exposed on the end surface of
the opening end. Therefore, in the battery case including a
nickel-plated layer, crevice corrosion proceeds between the
substrate layer and the nickel-plated layer due to a contact with
the body fluid. In the case that the plated layer of the present
invention is used, however, reaction products of tin or zinc
suppress the shift of the inside of the crevice to a strong acid
side, thereby delaying the crevice corrosion.
As the plated layer disposed on the outer surface, a nickel-zinc
plated layer is preferable because it has a high hardness. In the
sealing plate, a nickel-zinc plated layer or a zinc-tin plated
layer is preferable because it has a high hydrogenating voltage and
has a great effect of suppressing hydrogen generation.
The plated layer includes at least two metals selected from a set
consisting of nickel, zinc, and tin. In the case that the plated
layer includes nickel--as the essential metal--and another metal,
namely in the case that a nickel-zinc plated layer or a nickel-tin
plated layer is produced, the amount of nickel is preferably 30
mass % or less in the composition of the plated layer. When the
percentage of nickel is higher than 30 mass %, the anti-corrosion
effect by a local battery is reduced to promote the corrosion
reaction of the nickel. While, when the percentage of nickel is
lower than 5 mass % for example, the dissolution of zinc or tin by
a corrosion reaction and the dissolving reaction by alkali are apt
to occur. Therefore, the effect of suppressing the water
electrolysis reaction reduces. Thus, the amount of nickel is more
preferably 5 to 20 mass %, still more preferably 7 to 17 mass
%.
In the case of producing a zinc-tin plated layer including zinc and
tin as the two metals, the amount of zinc is preferably 35 mass %
or less in the composition of the plated layer. When the percentage
of zinc is higher than 35 mass %, the plated layer is difficult to
be produced. While, when the percentage of zinc is lower than 1
mass % for example, an oxidation reaction of tin is apt to occur,
thereby increasing the contact resistance on a battery surface. On
the positive electrode side, the dissolving reaction of tin is apt
to proceed, thereby reducing the effect of suppressing the water
electrolysis reaction. Therefore, the percentage of zinc is
preferably 1 to 30 mass %, more preferably 5 to 15 mass %.
The plated layer may include nickel, zinc, and tin. In this case,
preferably, the percentages of zinc and tin are adjusted so as to
be the above-mentioned percentages for the same reason.
Preferably, the amount of nickel is adjusted so that the percentage
of nickel in the whole plated layer is 1 to 10 mass %.
The thickness of the plated layer is preferably 0.5 to 10 .mu.m,
more preferably 1 to 3 .mu.m. On the outer surface or inner surface
of this plated layer, a nickel-plated layer may be further
disposed. Nickel has a great effect of reducing the contact
resistance, and is easily dissolved in the environment in a living
body. Therefore, in case of disposing the nickel plate on the outer
surface, the plated layer of the present invention is rapidly
exposed in the living body, so that, the abovementioned function is
not inhibited. While, in case of disposing the nickel plate on the
inner surface, heat treatment, for example, result in that the
nickel is alloyed with the substrate layer or the plated layer of
the present invention. Therefore, a thin material can be produced,
so that the contact resistance between the substrate layer and the
plated layer of the present invention can be reduced, and the
long-term use performance of the battery can be improved.
Preferably, the thickness of the nickel-plated layer is 1 to 3
.mu.m.
The substrate layer of the sealing plate is a main material forming
the frame of the sealing plate. In order to obtain a frame of a
high strength, it is preferable to employ at least one selected
from a set consisting of stainless steel, ordinary steel, and
carbon steel. In order to keep the corrosion resistance to a power
generation element and suppress the increase in the internal
resistance, it is preferable to employ stainless steel. The
substrate layer may be a laminated body of stainless steel, and
ordinary steel and/or carbon steel. Types of the stainless steel
include: 400-series ferritic stainless steel such as SUS430,
SUS444, or SUS447; 300-series austenitic stainless steel such as
SUS304, SUS305, or SUS316; and two-phase stainless steel such as
SUS329. A nickel alloy such as NAS254 or NAS354 having a
composition similar to that of the stainless steel may be
employed.
The ordinary steel is steel such as an SS material, an SM material,
and an SPCC material defined by Japanese Industrial Standards
(JIS). The carbon steel is steel such as S10C, S20C, S30C, S45C,
and S55C, and belongs to a mechanical structural alloy steel. When
the ordinary steel or carbon steel is employed for the substrate
layer of the battery, however, it is desirable that a nickel-plated
layer for corrosion prevention is produced on the inside of the
battery.
The substrate layer of the battery case is not particularly limited
as long as it has a corrosion resistance and strength. Stainless
steel, ordinary steel, carbon steel, titanium, cladding material
(for example, cladding material of aluminum and stainless steel)
can be employed.
Hereinafter, a coin type battery of the embodiment of the present
invention is described with reference to the accompanying drawing.
However, the following embodiment does not limit the technological
scope of the present invention.
Power generation elements are stored in the exterior body. The
power generation elements include positive electrode 2, negative
electrode 3, separator 4, and an electrolyte (not shown). In the
shown example, positive electrode 2 is disposed so as to face
bottom plate 1a of battery case 1. Battery case 1 serves as a
positive electrode terminal. While, negative electrode 3 is
disposed so as to face top plate 6a of sealing plate 6. Sealing
plate 6 serves as a negative electrode terminal
As the material of battery case 1, preferably, a metal plate having
a corrosion resistance at a positive electrode potential is
employed as a substrate layer. For example, it is preferable that
stainless steel (for example, SUS430, SUS444, or SUS329J) is
employed for battery case 1 of a lithium battery. Furthermore, it
is preferable to employ a material (not shown in FIG. 1) having, on
its outer surface, a plated layer that includes at least two metals
selected from a set consisting of nickel, zinc, and tin.
Preferably, the materials of sealing plate 6 include: stainless
steel, ordinary steel, or carbon steel as substrate layer 61; and a
material having, on its outer surface, plated layer 62 including at
least two metals selected from a set consisting of nickel, zinc,
and tin. As substrate layer 61, it is preferable to employ
stainless steel (for example, SUS304, SUS316, or SUS430) because it
is stable for lithium metals.
In the case of accidental ingestion of the coin type battery into a
living body, a local battery is produced between different metals
included in the plated layer, thereby suppressing the dissolution
of the plated layer. Therefore, when the plated layer is disposed
on the sealing plate, the hydrogen generation around the negative
electrode is suppressed, thereby reducing the shift to a strong
alkaline side. While, when the plated layer is disposed on the
battery case, the corrosion resistance of the metals included in
the plated layer is suppressed, thereby reducing the shift to a
strong acid side.
Next, taking a lithium battery as an example, a manufacturing
method of a coin type battery is described. The manufacturing
method of the coin type battery includes the following
processes:
(a) preparing power generation elements;
(b) preparing a battery case;
(c) preparing a sealing plate;
(d) preparing a gasket; and
(e) storing the power generation elements in the battery case,
blocking the opening in the battery case with the sealing plate,
and caulking the opening end of the battery case to a rim portion
of the sealing plate via the gasket.
The thickness of the material used for the sealing plate is 0.2 to
0.3 mm, for example. The thickness of the material used for the
battery case is 0.1 to 0.3 mm, for example.
In process (b), a battery case is produced by drawing stainless
steel having a plated layer on its surface into a bottomed
cylindrical shape so that the plated layer forms the outer surface.
The plated layer is, for example, a nickel-zinc plated layer, a
nickel-tin plated layer, or a zinc-tin plated layer.
In process (c), a sealing plate having a predetermined shape is
produced, by pressing stainless steel that has a plated layer on
its surface so that the plated layer forms the outer surface. The
plated layer is, for example, a nickel-zinc plated layer, a
nickel-tin plated layer, or a zinc-tin plated layer.
In process (d), a gasket is prepared which has an annular groove
engaging with the rim portion of the sealing plate. The gasket may
be previously mounted on the rim portion of the sealing plate. As
the material of the gasket, polypropylene (PP), polyphenylene
sulfide (PPS), or polyether ether ketone (PEEK) can be employed,
for example.
In process (e), the power generation elements are stored in the
battery case, and the sealing plate is disposed so as to block the
opening in the battery case. Then, the opening end of the battery
case is folded inward. Thus, the gasket is compressed, and the
lower end of the gasket tightly comes into contact with the bottom
plate of the battery case. The upper end of the gasket tightly
comes into contact with the rim portion of the sealing plate.
Next, taking a lithium battery as an example, the power generation
elements of the coin type battery are described.
A positive electrode is produced by pressure-forming a positive
electrode material mixture into a coin shape. The positive
electrode material mixture includes a positive electrode active
material, a conductive auxiliary agent, and a binder. The type of
the positive electrode active material is not especially limited,
but may be an oxide (for example, manganese dioxide) or composite
oxide that contains at least one selected from a set consisting of
transition metals such as manganese, cobalt, nickel, magnesium,
copper, iron, and niobium. Alternatively, a composite oxide (for
example, LiCoO.sub.2) may be employed which contains lithium and at
least one selected from a set consisting of metals such as
manganese, cobalt, nickel, magnesium, copper, iron, and niobium.
Alternatively, graphite fluoride may be employed. The positive
electrode active materials may be employed singly or in
combination.
As the conductive auxiliary agent, carbon black such as acetylene
black or ketjen black, or graphite such as artificial graphite can
be employed. The conductive auxiliary agents may be employed singly
or in combination.
As the binder, fluorine resin, styrene-butadiene rubber (SBR),
modified acrylonitrile rubber, or ethylene-acrylic acid copolymer
is employed, for example. The binders may be employed singly or in
combination.
The negative electrode includes a lithium metal or lithium alloy
molded in a coin shape, for example. As the lithium alloy, a Li--Al
alloy, a Li--Sn alloy, a Li--Si alloy, or a Li--Pb alloy is
employed. The negative electrode may be produced by
pressure-forming, into a coin shape, a negative electrode material
mixture that contains a negative electrode active material and a
binder. The type of the negative electrode active material is not
especially limited. However, examples of the negative electrode
active material include: a carbon material such as natural
graphite, artificial graphite, or non-graphitizable carbon; and a
metal oxide such as silicon oxide, lithium titanate, niobium
pentoxide, or molybdenum dioxide. As the binder, the above
mentioned material available for the positive electrode can be
optionally employed, for example. The negative electrode material
mixture may contain a conductive auxiliary agent.
The electrolyte includes a nonaqueous solvent, and a solute (salt)
dissolving in the nonaqueous solvent. Preferably, the solute
concentration in the electrolyte is 0.3 to 2.0 mol/L. As the
nonaqueous solvent, cyclic carbonate, chain carbonate, chain ether,
or cyclic ether can be employed. These nonaqueous solvents may be
employed singly or in combination. As the solute, LiBF.sub.4,
LiPF.sub.6, LiClO.sub.4, LiCF.sub.3SO.sub.3,
LiC.sub.4F.sub.9SO.sub.3, LiN(CF.sub.3SO.sub.2).sub.2, or
LiN(C.sub.2F.sub.5SO.sub.2).sub.2 is employed.
The separator may be made of any material as long as the material
can prevent a short circuit between the positive electrode and the
negative electrode. For example, woven fabric, nonwoven fabric, or
microporous film made of polyolefin or polyester is employed.
Next, the present invention is specifically described on the basis
of examples. However, the following examples do not limit the
present invention.
EXAMPLE 1
In the present example, a coin type battery having a structure
shown in FIG. 1 is produced.
(1) Battery Case
As a material of battery case 1, a stainless steel plate (SUS430)
of a thickness of 200 .mu.m is prepared which has a nickel-plated
layer of a thickness of 1 .mu.m. By drawing this material so that
the nickel-plated layer is disposed on the outer surface side,
battery case 1 is produced in which the diameter of the bottom
plate is 20 mm and the height of side portion 1b is 2.8 mm
(2) Sealing Plate
A material is prepared in which nickel-zinc plated layer 62 of a
thickness of 3 .mu.m is produced on a surface of a stainless steel
plate (SUS430) of a thickness of 250 .mu.m. The stainless steel
plate serves as substrate layer 61. Nickel-zinc plated layer 62 is
produced so as to contain nickel by 12 mass %. By pressing this
material so that nickel-zinc plated layer 62 forms the outer
surface, sealing plate 6 in which the diameter of top plate 6a is
17 mm is produced.
(3) Power Generation Element
A positive electrode material mixture is prepared, by mixing 100
ptsmass of manganese dioxide as a positive electrode active
material, 7 ptsmass of graphite as a conductive auxiliary agent,
and 5 ptsmass of polytetrafluoroethylene as a binder. Positive
electrode 2 is produced by molding the positive electrode material
mixture into a coin shape of a diameter of 15 mm and a thickness of
2 mm. While, a negative electrode is produced by punching a metal
lithium foil of a thickness of 0.6 mm into a circular shape of a
diameter of 16 mm. As the electrolyte, an organic electrolyte is
produced by dissolving, at a concentration of 1.0 mol/L,
LiClO.sub.4 as a solute in a nonaqueous solvent. The nonaqueous
solvent is obtained by mixing propylene carbonate and
1,2-dimethoxyethane at a volume ratio of 2:1.
(4) Assembling of Coin Type Battery
Gasket 5 that is made of polypropylene and is coated with a sealant
made of blown asphalt and mineral oil is disposed inside side
portion 1b of battery case 1, a current collector made of SUS430 is
disposed on bottom plate 1a, and positive electrode 2 is disposed
on the current collector. Next, polypropylene-made nonwoven fabric
of a thickness of 300 .mu.m is disposed as separator 4 on positive
electrode 2. Then, the organic electrolyte is injected into battery
case 1. Negative electrode 3 is pasted on the inside of top plate
6a of sealing plate 6. Next, sealing plate 6 is disposed so as to
block the opening in battery case 1, and the end of side portion 1b
of battery case 1 is caulked to rim portion 6b of sealing plate 6
via gasket 5. Thus, coin type battery A1 having a diameter of 20
mm, a thickness of 3.2 mm, and a capacity of 225 mAh is
completed.
Next, coin type battery A2 is completed as in the case of battery
A1 except that a nickel-tin plated layer containing nickel by 12
mass % is produced instead of a nickel-zinc plated layer disposed
on the outer surface of the sealing plate. Next, coin type battery
A3 is completed as in the case of battery A1 except that a zinc-tin
plated layer containing zinc by 12 mass % is produced instead of a
nickel-zinc plated layer disposed on the outer surface of the
sealing plate.
Furthermore, coin type battery B1 is completed as in the case of
battery A1 except that a nickel-plated layer is produced instead of
a nickel-zinc plated layer disposed on the outer surface of the
sealing plate.
[Evaluation]
Thus, 10 coin type batteries A1, 10 coin type batteries A2, 10 coin
type batteries A3, and 10 coin type batteries B1 are prepared.
Processed meat (ham) made of pork is placed on the bottom of a
petri dish of a depth of 15 mm. Then, instead of the body fluid,
normal saline is poured into the petri dish to completely dip the
ham into the normal saline. Then, a battery to be evaluated is
mounted on the ham so that the sealing plate comes into contact
with the ham. At this time, the bottom surface of the battery case
is set slightly lower than the liquid level of the normal saline so
that the battery does not float, thereby creating the state in
which a film of the saline is formed on the case bottom surface.
This state is kept at 25.degree. C. for 30 minutes. Then, the state
of the contact part of the ham with the sealing plate is observed
visually. At this time, discoloration is hardly observed in the ham
on which each of batteries A1, A2, and A3 is mounted. While, a
strong discoloration is observed in the ham on which battery B1 is
mounted. Ten batteries in each example show the same trend.
Next, the pH of the contact surface of the ham with the sealing
plate is measured, and the average value of 10 values is
calculated. The result is shown in Table 1. Battery B1 indicates a
strong alkalinity. However, the shift to an alkaline side is
suppressed in each of batteries A1, A2, and A3 that have a
nickel-zinc plated layer, nickel-tin plated layer, or zinc-tin
plated layer on the outer surface of the sealing plate.
TABLE-US-00001 TABLE 1 A1 A2 A3 B1 Plated layer on Nickel-zinc
Nickel-tin Zinc-tin Nickel sealing plate Plated layer on Nickel
Nickel Nickel Nickel battery case Discoloration Almost no Almost no
Almost no Strong pH 6.8 6.7 6.9 >14
EXAMPLE 2
Coin type batteries A4 to A9 are produced as in the case of battery
A1 except that the composition of the nickel-zinc plated layer is
changed, and an evaluation similar to that in example 1 is applied
to them. The result is shown in Table 2. In batteries A4 to A7, the
pH is stable similarly to battery A1. While, in battery A8 having a
large amount of nickel and battery A9 having a small amount of
nickel, the pH shifts to an alkaline side. Discoloration is hardly
observed in the ham on which each of batteries A4 to A7 is mounted,
but slight discoloration is observed in the ham on which each of
batteries A8 and A9 is mounted. Ten batteries in each example show
the same trend. This is probably because increase in the percentage
of nickel or zinc reduces the anti-corrosion effect by a local
battery between nickel and zinc, causes the elution of nickel or
zinc, and increases the amount of generation of hydrogen.
TABLE-US-00002 TABLE 2 A1 A4 A5 A6 A7 A8 A9 Amount 12 20 17 7 5 30
3 of nickel in plated body (%) Amount 88 80 83 93 95 70 97 of zinc
in plated body (%) Discolor- Almost Almost Almost Almost Almost
Slight Slight ation no no no no no pH 6.8 6.8 6.7 6.8 7 8.7 9.3
A nickel-zinc plated layer is produced on the outer surface of the
sealing plate in example 2, but a similar trend is considered to be
obtained even when a nickel-tin plated layer is formed.
EXAMPLE 3
Coin type battery A10 is produced as in the case of battery B1
except that a material having a nickel-zinc plated layer of a
thickness of 1 .mu.m is used on the surface of a stainless steel
plate (SUS430) of a thickness of 200 .mu.m as a substrate layer in
the battery case. At this time, the nickel-zinc plated layer is
produced so as to contain nickel by 12 mass %.
Next, coin type battery A11 is produced as in the case of battery
A10 except that a sealing plate having a nickel-zinc plated layer
is used similarly to battery A1.
Next, coin type battery A12 is completed as in the case of battery
A10 except that, instead of the nickel-zinc plated layer on the
battery case, a nickel-tin plated layer containing nickel by 12
mass % is produced.
Next, coin type battery A13 is completed as in the case of battery
A10 except that, instead of the nickel-zinc plated layer on the
battery case, a zinc-tin plated layer containing zinc by 12 mass %
is produced.
An evaluation similar to that in example 1 is applied to batteries
A10 to A13. The result is shown in Table 3.
In each of batteries A10 to A13 having a nickel-zinc plated layer,
nickel-tin plated layer, or zinc-tin plated layer on the outer
surface of the battery case, the shift to an acid side is
suppressed. Especially, battery A11 having a nickel-zinc plated
layer on both of the battery case and sealing plate indicates a
value closer to the neutral.
Thus, it is clear that producing the above-mentioned plated layer
on at least one of the sealing plate and battery case can
significantly reduce the damage to the living body even in the case
of accidental ingestion of the coin type battery into a living
body.
TABLE-US-00003 TABLE 3 A10 A11 A12 A13 Plated layer on Nickel
Nickel-zinc Nickel Nickel sealing plate Plated layer on Nickel-zinc
Nickel-zinc Nickel-tin Zinc-tin battery case Discoloration Almost
no Almost no Almost no Almost no pH 7.6 6.9 7.8 7.9
The present invention can be applied to various batteries--such as
a lithium battery, an alkaline battery, and an alkaline storage
battery--including a primary battery and secondary battery. The
present invention is especially useful for a battery (for example,
lithium battery) having a battery voltage higher than 3.0 V.
* * * * *